Nanoparticle backside die adhesion layer

ABSTRACT

In described examples, a microelectronic device includes a microelectronic die with a die attach surface. The microelectronic device further includes a nanoparticle layer coupled to the die attach surface. The nanoparticle layer may be in direct contact with the die attach surface, or may be coupled to the die attach surface through an intermediate layer, such as an adhesion layer or a contact metal layer. The nanoparticle layer includes nanoparticles having adjacent nanoparticles adhered to each other. The microelectronic die is attached to a package substrate by a die attach material. The die attach material extends into the nanoparticle layer and contacts at least a portion of the nanoparticles.

TECHNICAL FIELD

This application is a division of U.S. patent application Ser. No.15/914,761, filed Mar. 7, 2018, the contents of all of which are hereinincorporated by reference in its entirety.

This relates generally to microelectronic devices, and more particularlyto adhesion layers for assembly of microelectronic devices.

BACKGROUND

A microelectronic device may include a die that is attached to a packagesubstrate at a die attach surface of the die. The die may be attached tothe package substrate by a die attach material, such as an adhesive orsolder. The die attach surface may be smooth, as a result of fabricationprocesses, such as backgrinding, used to make the die. The smoothness ofthe die attach surface may provide limited mechanical support foradhesion of the die attach material. Stress between die and the packagesubstrate, such as resulting from thermal expansion, may cause the dieattach material to separate from the die attach surface, undesirablydegrading performance of the microelectronic device.

SUMMARY

In described examples, a microelectronic device includes amicroelectronic die with a die attach surface. The microelectronic dieis attached to a package substrate of the microelectronic device by adie attach material. The microelectronic device includes a nanoparticlelayer coupled to the die attach surface. The nanoparticle layer includesnanoparticles. Adjacent nanoparticles are adhered to each other. The dieattach material extends into the nanoparticle layer and contacts atleast a portion of the nanoparticles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are cross-sections of an example microelectronicdevice.

FIG. 2A and FIG. 2B are cross-sections of another examplemicroelectronic device.

FIG. 3A through FIG. 3E depict a microelectronic device in stages of anexample method of formation.

FIG. 4A through FIG. 4E depict a microelectronic device in stages ofanother example method of formation.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The drawings are not necessarily drawn to scale. Example embodiments arenot limited by the illustrated ordering of acts or events, as some actsor events may occur in different orders and/or concurrently with otheracts or events. Furthermore, not all illustrated acts or events arerequired to implement a methodology in accordance with exampleembodiments.

A microelectronic device includes a microelectronic die, such as asilicon integrated circuit, a device having a substrate of a compoundsemiconductor material (such as silicon carbide, gallium nitride, orgallium arsenide), a microelectronic mechanical system (MEMS) device, anoptoelectronic device, or a discrete semiconductor component (such as apower transistor). The microelectronic die has a die attach surface,such as a surface opposite from a component surface, the componentsurface having bond pads coupled to various components of themicroelectronic die. Material of the microelectronic die at the dieattach surface may be electrically conductive or semiconducting, such asmetal or semiconductor material. Alternatively, the material of themicroelectronic die at the die attach surface may be electricallynonconductive or semi-insulating, such as sapphire, glass, undopedgallium nitride, or high purity silicon. The microelectronic deviceincludes a package substrate, such as a die pad of a lead frame, or adie pad of a ceramic chip carrier. The microelectronic die is attachedto the package substrate by a die attach material. The die attachmaterial may be electrically conductive, such as solder or adhesivecontaining electrically conductive particles of metal or carbon.Alternatively, the die attach material may be electricallynonconductive, such as a polymer adhesive free of electricallyconductive particles. The microelectronic device includes a nanoparticlelayer coupled to the die attach surface. The nanoparticle layer includesnanoparticles. Adjacent nanoparticles are adhered to each other. Thenanoparticle layer may be directly coupled to the die attach surface, ormay be coupled to the die attach surface through an intermediate layer,such as an adhesion layer or a contact metal layer, having metal,aluminum oxide or similar material. The nanoparticles attach to theintermediate layer (if present) by molecular bonds, such as metallicbonds, covalent bonds, or similar bonds. The die attach material extendsinto the nanoparticle layer and contacts at least a portion of thenanoparticles. Mechanical adhesion of the die attach material to the dieattach surface may be advantageously higher than a comparablemicroelectronic device with no nanoparticle layer, because the dieattach material contacts the nanoparticles in an interlockingconfiguration. Separation of the die attach surface from the packagesubstrate due to stress may thus be reduced or avoided, and soreliability of the microelectronic device may thus be improved.

For the purposes of this disclosure, if an element is referred to asbeing “coupled” to another element, it may be directly coupled to theother element, or intervening elements may exist. If an element isreferred to as being “directly coupled” to another element, no otherintervening elements are intentionally disposed. Similarly, if anelement is referred to as being “on” another element, it may be directlyon the other element, or intervening elements may exist. If an elementis referred to as being “directly on” another element, no otherintervening elements are intentionally disposed.

FIG. 1A and FIG. 1B are cross-sections of an example microelectronicdevice 100. The microelectronic device 100 includes a microelectronicdie 102. The microelectronic die 102 has a die attach surface 104. Themicroelectronic die 102 of this example further has a component surface106 opposite from the die attach surface 104. Bond pads 108 are locatedat the component surface 106. The bond pads 108 are electrically coupledto components of the microelectronic die 102. For example, themicroelectronic die 102 may be an integrated circuit, a discrete device(such as a power transistor), an optoelectronic device, or a MEMSdevice. Also for example, material of the microelectronic die 102extending to the die attach surface 104 may include silicon, galliumnitride, gallium arsenide, silicon carbide, sapphire, or glass.

In this example, the microelectronic device 100 includes an intermediatelayer 110 directly contacting the die attach surface 104. For example,the intermediate layer 110 may include one or more metal layers such asa layer stack of titanium, nickel, and silver, which exhibits desiredadhesion to silicon surfaces. Metal in the intermediate layer 110 mayreduce a sheet resistance of a substrate of the microelectronic die 102,advantageously reducing debiasing of regions of the substrate due tolateral currents in the substrate. The intermediate layer 110 mayinclude one or more dielectric materials (such as aluminum oxide orsilicon monoxide), which exhibit desired adhesion to dielectricsurfaces. Other materials for the intermediate layer 110 are within thescope of this example.

The microelectronic device 100 includes a nanoparticle layer 112 coupledto the die attach surface 104. In this example, the nanoparticle layer112 directly contacts the intermediate layer 110, and so is coupled tothe die attach surface 104 through the intermediate layer 110. Thenanoparticle layer 112 may extend continuously across the die attachsurface 104, as depicted in FIG. 1A. The nanoparticle layer 112 includesnanoparticles 114, as depicted in FIG. 1B. Adjacent nanoparticles 114are adhered to each other. The nanoparticles 114 may includeelectrically conductive materials (such as metals and graphene), so thatthe nanoparticle layer 112 is electrically conductive. Some instances ofthe nanoparticles 114 may have cores of metal (such as copper),surrounded by one or more layers of oxidation-resistant metal (such asnickel, silver or gold). Other instances of the nanoparticles 114 mayhave cores of dielectric material, such as aluminum oxide or silicondioxide, surrounded by one or more layers of oxidation-resistant metal.Further instances of the nanoparticles 114 may be electricallynonconductive and may include ceramic materials, such as oxides,carbides, or nitrides. Other compositions and structures of thenanoparticles 114 are within the scope of this example. The nanoparticlelayer 112 may include binder material, such as silicon-containingmolecules, providing adhesion between the adjacent nanoparticles 114.

The microelectronic device 100 includes a package substrate 116. Forexample, the package substrate 116 may include metal, ceramic, glass,printed circuit board material such as (fiberglass reinforced plastic),or other material appropriate for supporting the microelectronic die102. A surface of the package substrate 116 facing the microelectronicdie 102 may be electrically conductive, or electrically nonconductive.The package substrate 116 may be part of a lead frame 118, which mayinclude external leads 120. The bond pads 108 may be electricallycoupled to the external leads 120 by wire bonds 122, as depicted in FIG.1A.

The microelectronic die 102 is attached to the package substrate 116 bya die attach material 124. In this example, the die attach material 124directly contacts the package substrate 116. The die attach material 124extends into the nanoparticle layer 112 and contacts at least a portionof the nanoparticles 114. Some instances of the die attach material 124may include an adhesive material, such as epoxy or urethane. Instancesof the die attach material 124 which include the adhesive material mayalso include electrically conductive particles such as silver particles,nickel particles, carbon particles, nickel-coated copper particles, orsimilar particles, to provide electrical conductivity in the die attachmaterial 124. Other instances of the die attach material 124 may includeprimarily solder, and so may include mixtures of metals such as zinc,bismuth, tin, indium, or antimony.

In versions of this example, the material of the microelectronic die 102at the die attach surface 104, the intermediate layer 110 (if present),the nanoparticle layer 112, the die attach material 124, and the packagesubstrate 116 are electrically conductive. Those versions may providedesired electrical coupling of the microelectronic die 102 to thepackage substrate 116, such as to provide a substrate bias to themicroelectronic die 102 during operation of the microelectronic device100. Alternately, in other versions of this example, any of the materialof the microelectronic die 102 at the die attach surface 104, theintermediate layer 110 (if present), the nanoparticle layer 112, the dieattach material 124, and the package substrate 116 are electricallynonconductive. Those versions may provide a desired electrical isolationof the microelectronic die 102 at the die attach surface 104.

The microelectronic device 100 may further include one or more packageelements, such as an encapsulation material 126 around themicroelectronic die 102 and the package substrate 116. Other packageelements, such as a metal lid over the microelectronic die 102, arewithin the scope of this example.

FIG. 2A and FIG. 2B are cross-sections of another examplemicroelectronic device 200. The microelectronic device 200 includes amicroelectronic die 202. The microelectronic die 202 has: (a) a dieattach surface 204; and (b) a component surface 206 opposite from thedie attach surface 204. Bond pads 208 are located at the componentsurface 206. The microelectronic die 202 may be manifested as any of thedevices disclosed in reference to the microelectronic die 102 of FIG.1A.

In this example, the microelectronic device 200 includes a lead frame218. The bond pads 208 are electrically coupled to the lead frame 218 bybump bonds 222. The microelectronic device 200 further includes apackage substrate 216, which (in this example) is a clip 216electrically coupled to the lead frame 218.

The microelectronic device 200 includes a nanoparticle layer 212 coupledto the die attach surface 204. In this example, the nanoparticle layer212 directly contacts the die attach surface 204. The nanoparticle layer212 includes nanoparticles 214, as depicted in FIG. 2B. Adjacentnanoparticles 214 are adhered to each other. The nanoparticles 214 mayhave any of the compositions and structures disclosed with regard to thenanoparticles 114 of FIG. 1B. The nanoparticle layer 212 may optionallyinclude binder material.

The microelectronic die 202 is attached to the package substrate 216 bya die attach material 224. In this example, the die attach material 224directly contacts the package substrate 216. The die attach material 224extends into the nanoparticle layer 212 and contacts at least a portionof the nanoparticles 214. The die attach material 224 may include any ofthe materials disclosed with regard to the die attach material 124 ofFIG. 1A and FIG. 1B.

The nanoparticle layer 212 may be configured to cover a plurality ofareas of the die attach surface 204, with gaps 228 in the nanoparticlelayer 212 between the areas, as depicted in FIG. 2A and FIG. 2B. Inversions of this example, the nanoparticle layer 212 is electricallyconductive, and the different areas of the nanoparticle layer 212 mayalign with circuits in the microelectronic die 202 to reduce lateralcurrents in a substrate of the microelectronic die 202, which can causeunwanted debiasing of regions of the substrate. In other versions, thecombination of areas of the nanoparticle layer 212 and the gaps 228between the areas may result from a patterned configuration for thenanoparticle layer 212 that balances adhesion to the die attach material224 and cost of forming the nanoparticle layer 212.

The microelectronic device 200 may further include one or more packageelements, such as an encapsulation material 226 around themicroelectronic die 202 and the package substrate 216. Other packageelements, such as a metal lid over the microelectronic die 202, arewithin the scope of this example.

FIG. 3A through FIG. 3E depict a microelectronic device 300 in stages ofan example method of formation. Referring to FIG. 3A, a microelectronicsubstrate 330 includes a microelectronic die 302 of the microelectronicdevice 300, and may include additional microelectronic die 332. Themicroelectronic substrate 330 has: (a) a die attach surface 304; and (b)a component surface 306 opposite from the die attach surface 304. Themicroelectronic die 302 may include components (such as transistors orMEMS components) proximate to the component surface 306. For example,the microelectronic substrate 330 may be a semiconductor wafer (such asa silicon wafer), a silicon-on-insulator (SOI) wafer, a gallium nitridewafer, a gallium arsenide wafer, a sapphire wafer, or other substrateappropriate for forming the microelectronic die 302.

Nanoparticle layers 312 are formed on the die attach surface 304. Thenanoparticle layers 312 may be formed directly on the die attach surface304, as depicted in FIG. 3A, or may be coupled to the die attach surface304 through an optional intermediate layer (not shown in FIG. 3A). Thenanoparticle layers 312 may be patterned, as depicted in FIG. 3A, or maycompletely cover the die attach surface 304 of the microelectronic die302 and of the additional microelectronic die 332.

The nanoparticle layers 312 may be formed by an additive process 334that dispenses a nanoparticle dispersion 336 onto the die attach surface304. FIG. 3A depicts the additive process 334 partway through formingthe nanoparticle layers 312 on each of the microelectronic die 302 andof the additional microelectronic die 332. The nanoparticle dispersion336 includes nanoparticles, such as having the compositions disclosedwith regard to the nanoparticles 114 of FIG. 1B. The nanoparticledispersion 336 may further include a binder material to improve adhesionbetween the nanoparticles, or may include a volatile material to improvedispensing properties of the nanoparticle dispersion 336. For example,the additive process 334 may include an inkjet process, represented inFIG. 3A by an inkjet dispense head 338. Examples of other additiveprocesses include binder jetting, directed energy deposition, materialextrusion, material jetting, powder bed fusion, sheet lamination, vatphotopolymerization, direct laser deposition, electrostatic deposition,laser sintering, electrochemical deposition, and photo-polymerizationextrusion. The additive process 334 disposes the nanoparticle dispersion336 in a desired area for the nanoparticle layers 312 and does notdispose the nanoparticle dispersion 336 outside of the desired area, sothat it is not necessary to remove a portion of the dispensednanoparticle dispersion 336 to produce a final desired shape of thenanoparticle layers 312. The nanoparticle layers 312 have a matrix ofnanoparticles, which is efficiently realized by the additive process.Moreover, additive processes may enable forming the nanoparticle layers312 in desired areas without photolithographic processes and subsequentetch processes, thus advantageously reducing fabrication cost andcomplexity.

Referring to FIG. 3B, the nanoparticle layers 312 may be heated toremove volatile material from the nanoparticle layers 312, to cure orpolymerize binder material in the nanoparticle layers 312, or to formmolecular bonds between adjacent nanoparticles in the nanoparticlelayers 312, so that adjacent nanoparticles are adhered to each other.The nanoparticle layers 312 may be heated by a radiant heat process 340as indicated in FIG. 3B, or may be heated by a hotplate process, afurnace process, a xenon flashbulb process, or other heating method. Inversions of this example: (a) the nanoparticle layers 312 are patterned;and (b) the nanoparticle layers 312 may be heated by a scanned radiantheating process, such as using light emitting diodes (LEDs), to avoidheating the microelectronic substrate 330 where exposed by thenanoparticle layers 312. This advantageously reduces thermal degradationof components in the microelectronic die 302 and of the additionalmicroelectronic die 332.

Referring to FIG. 3C, the microelectronic die 302 and the additionalmicroelectronic die 332 are singulated, so they are separated from eachother. The microelectronic die 302 and the additional microelectronicdie 332 may be singulated by sawing the microelectronic substrate 330,by mechanically scribing the microelectronic substrate 330, by laserscribing the microelectronic substrate 330, by etching themicroelectronic substrate 330 between the microelectronic die 302 andthe additional microelectronic die 332, or by other singulation process.After the microelectronic die 302 and the additional microelectronic die332 are singulated, the microelectronic die 302 and the additionalmicroelectronic die 332 may be separated for assembly.

Referring to FIG. 3D, a layer of die attach material 324 is disposed ona package substrate 316 of a lead frame 318. The package substrate 316may be a die attach area of the lead frame 318. The layer of die attachmaterial 324 may be a solder preform, or other die attach material. Thelead frame 318 may be a portion of a lead frame array, connected toother lead frames by tie bars.

The microelectronic die 302 is disposed on the layer of die attachmaterial 324 so that the nanoparticle layer 312 directly contacts thelayer of die attach material 324. The microelectronic die 302 may bedisposed on the layer of die attach material 324, such as by a pick andplace operation.

Referring to FIG. 3E, the lead frame 318, the die attach material 324,the nanoparticle layer 312, which is hidden in FIG. 3E, and themicroelectronic die 302 are heated, causing the die attach material 324to attach to the package substrate 316 and to extend into, and attachto, the nanoparticle layer 312. In versions of this example, the dieattach material 324 is manifested as solder, and heating the die attachmaterial 324 causes the solder to reflow and harden upon subsequentcooling. In other versions, the die attach material 324 is manifested asa thermosetting adhesive, and heating the die attach material 324 causesthe adhesive to cure or set. In some versions, the die attach material324 is manifested as a thermoplastic adhesive, and heating the dieattach material 324 causes the adhesive to have a lower viscosity andflow into the nanoparticle layer, and become more viscous uponsubsequent cooling. The lead frame 318, the die attach material 324, thenanoparticle layer 312, and the microelectronic die 302 may be heated bya radiant heat process 342, as depicted in FIG. 3E, or by anotherheating process such as a hot plate process, a furnace process, orsimilar process.

The microelectronic device 300, which includes the microelectronic die302 attached to the package substrate 316 by the die attach material 324through the nanoparticle layer 312, may be further formed by addingpackage elements (e.g., encapsulation material or mechanical packageelements such as a lid). Other methods of further forming themicroelectronic device 300 are within the scope of this example, andother package elements of the microelectronic device 300 are within thescope of this example.

FIG. 4A through FIG. 4E depict a microelectronic device 400 in stages ofanother example method of formation. Referring to FIG. 4A, amicroelectronic substrate 430 includes a microelectronic die 402 of themicroelectronic device 400, and additional microelectronic die 432. Themicroelectronic substrate 430 has: (a) a die attach surface 404 and (b)a component surface 406 opposite from the die attach surface 404. Themicroelectronic die 402 may include components proximate to thecomponent surface 406.

In this example, an intermediate layer 410 is formed on the die attachsurface 404. The intermediate layer 410 may have a composition andelectrical conductivity as disclosed with regard to the intermediatelayer 110 of FIG. 1A and FIG. 1B. The intermediate layer 410 may beformed by the same facility that formed the components in themicroelectronic die 402 and additional microelectronic die 432, or maybe formed in a separate facility, such as an assembly facility that willassemble the microelectronic die 402 into the subsequently formedmicroelectronic device 400.

Nanoparticle dispersion 436 is dispensed onto the intermediate layer410, such as by a spin-coat apparatus 444 as depicted in FIG. 4A. Thenanoparticle dispersion 436 includes nanoparticles, not shown in FIG.4A, along with one or more fluid components, such as solvent, bindermonomer, or adhesion promoter. The microelectronic substrate 430 is spunby the spin-coat apparatus 444 to spread the nanoparticle dispersion 436across the intermediate layer 410.

Referring to FIG. 4B, the microelectronic substrate 430 is heated toremove volatile material from the nanoparticle dispersion 436 of FIG. 4Aand convert the nanoparticle dispersion 436 on the intermediate layer410 to a nanoparticle layer 412 in which adjacent nanoparticles areadhered to each other. The microelectronic substrate 430 may be heatedby a hot plate process using a heated chuck 446, as depicted in FIG. 4B.Other methods for heating the microelectronic substrate 430 are withinthe scope of this example.

Referring to FIG. 4C, the microelectronic die 402 and the additionalmicroelectronic die 432 are singulated. In FIG. 4C, the stack of themicroelectronic substrate 430, the intermediate layer 410, and thenanoparticle layer 412 are inverted with respect to FIG. 4B, to show thecomponent surface 406. Each of the microelectronic die 402 and theadditional microelectronic die 432 may have bond pads 408 proximate tothe component surface 406.

Referring to FIG. 4D, a layer of die attach material 424 is disposed ona package substrate 416 of a lead frame 418. The package substrate 416may be a die attach area of the lead frame 418. The layer of die attachmaterial 424 may be a portion of adhesive 424, as depicted in FIG. 4D,or other die attach material. The microelectronic die 402 is disposed onthe layer of die attach material 424 so that the nanoparticle layer 412directly contacts the layer of die attach material 424.

Referring to FIG. 4E, the lead frame 418, the die attach material 424,the intermediate layer 410, the nanoparticle layer 412, and themicroelectronic die 402 are heated, causing the die attach material 424to attach to the package substrate 416 and to extend into, and attachto, the nanoparticle layer 412. In versions of this example, the dieattach material 424 is manifested as a thermosetting adhesive, andheating the die attach material 424 causes the adhesive to cure or set.In some versions, the die attach material 424 is manifested as athermoplastic adhesive, heating the die attach material 424 causes theadhesive to have a lower viscosity and flow into the nanoparticle layerand become more viscous upon subsequent cooling. In other versions, thedie attach material 424 is manifested as solder, heating the die attachmaterial 424 causes the solder to reflow and harden upon subsequentcooling. The lead frame 418, the die attach material 424, thenanoparticle layer 412, and the microelectronic die 402 may be heated bya radiant heat process 442 applied above and below the microelectronicdevice 400, as depicted in FIG. 4E, or by another heating process.

The microelectronic device 400, which includes the microelectronic die402 attached to the package substrate 416 by the die attach material 424through the nanoparticle layer 412 and the intermediate layer 410, maybe further formed by adding package elements (e.g., encapsulationmaterial or mechanical package elements, such as a lid). Other methodsof further forming the microelectronic device 400 are within the scopeof this example, and other package elements of the microelectronicdevice 400 are within the scope of this example.

Modifications are possible in the described embodiments, and otherembodiments are possible, within the scope of the claims. Variousfeatures of the examples disclosed herein may be combined in othermanifestations of example microelectronic devices. For example, featuresdisclosed in reference to FIG. 1A and FIG. 1B may be combined with thestructure of FIG. 2A and FIG. 2B, and vice versa. Similarly, processesdisclosed in reference to FIG. 3A through FIG. 3E may be used in themethod disclosed in reference to FIG. 4A through FIG. 4E, and viceversa.

What is claimed is:
 1. A method of forming a microelectronic device, themethod comprising: providing a microelectronic substrate having a dieattach surface; and forming a nanoparticle layer coupled to and coveringa plurality of areas of the die attach surface, the nanoparticle layerincluding nanoparticles, wherein adjacent nanoparticles are adhered toeach other; providing a package substrate having a substrate interfacesurface coupled to the nanoparticle layer; forming a layer of die attachmaterial connecting the nanoparticle layer to the package substrate atthe substrate interface surface, wherein the die attach material extendsinto the nanoparticle layer and contacts at least a portion of thenanoparticles in an interlocking configuration.
 2. The method of claim1, in which there is a gap extending through the nanoparticle layer andthe die attach layer, the gap extending from the die attach surface tothe substrate interface surface.
 3. The method of claim 1, furthercomprising singulating microelectronic die after forming thenanoparticle layer.
 4. The method of claim 1, further comprising formingan intermediate layer on the die attach surface, wherein thenanoparticle layer is formed on the intermediate layer to contact thedie attach surface and to contact at least a portion of thenanoparticles.
 5. The method of claim 1, wherein forming thenanoparticle layer includes dispensing nanoparticle dispersion in apattern on the die attach surface.
 6. The method of claim 1, wherein atleast a portion of the nanoparticles are electrically conductive.
 7. Themethod of claim 1, wherein the nanoparticles are electricallyinsulating.
 8. The method of claim 1, wherein forming the nanoparticlelayer includes removing volatile material from the nanoparticle layer byheating the nanoparticle layer.
 9. The method of claim 1, whereinforming the nanoparticle layer includes adhering the adjacentnanoparticles by heating the nanoparticle layer.
 10. A method of forminga microelectronic device, the method comprising: providing amicroelectronic substrate including a microelectronic die with at leastone microelectronic component, the microelectronic substrate having adie attach surface; providing a nanoparticle layer coupled to the dieattach surface, the nanoparticle layer including nanoparticles, whereinadjacent nanoparticles are adhered to each other; providing a packagesubstrate; and forming a layer of a die attach material that connectsthe nanoparticle layer to the package substrate, wherein the die attachmaterial extends into the nanoparticle layer and contacts at least aportion of the nanoparticles in an interlocking configuration, andconfigured to increase a mechanical adhesion between the die attachsurface and the package substrate.
 11. The method of claim 10, whereinthe die attach material includes an adhesive material.
 12. The method ofclaim 10, wherein the die attach material includes solder.
 13. Themethod of claim 10, wherein forming the layer of the die attach materialincludes heating the die attach material after the die attach materialis in contact with the nanoparticle layer.
 14. A microelectronic device,comprising: a microelectronic die having a die attach surface; ananoparticle layer coupled to and covering areas of the die attachsurface, the nanoparticle layer including nanoparticles, whereinadjacent nanoparticles are adhered to each other; a package substrate;and a layer of a die attach material connecting the nanoparticle layerto the package substrate, wherein the die attach material extends intothe nanoparticle layer and contacts at least a portion of thenanoparticles; and a gap in and extending through the nanoparticle layerand the die attach material layer, the gap extending from the die attachsurface to the substrate interface surface.
 15. The microelectronicdevice of claim 14, further comprising a metal layer between the dieattach surface and the nanoparticle layer, wherein the metal layercontacts the die attach surface and contacts at least a portion of thenanoparticles.
 16. The microelectronic device of claim 14, wherein atleast a portion of the nanoparticles are electrically conductive. 17.The microelectronic device of claim 14, wherein at least a portion ofthe nanoparticles are electrically insulating.
 18. The microelectronicdevice of claim 14, wherein the die attach material includes an adhesivematerial.
 19. The microelectronic device of claim 14, wherein the dieattach material includes solder.